Salt stress tolerance in plants is induced by changes in molecular responses accompanied with alterations in the plant transcriptome, metabolome and proteome. Screening accessions for salt tolerance may be a rapid method of identifying which are most likely to survive when planted at salinized areas. To investigate the effects of salt stress on some accessions of Trachyspermum copticum, an experiment was conducted as factorial based on completely randomized design with three replications in the greenhouse. Studied factors included salt stress (0 and 100 mMol of NaCl) and ten accessions of ajwain (Shiraz, Esfahan, Hamadan, Zahedan, Tabriz, Mashhad1, Mashhad2, Yazd, Ahwaz and Arak). Based on the results, salt stress had decreasing effect on some morphological traits including main stem height, total fresh weight and total dry weight, 11.73, 44.66, 28.31 percent in comparison to control, respectively. There was a significant difference between the accessions in the measured traits, so that in the control, the highest main stem height was related to accessions of Hamedan (78.12 cm), the highest total fresh weight (22.84 gr) and the highest total dry weight (1.60 gr) related to accessions of Mashhad 1, also in 100 mMol of NaCl, the highest main stem height was related to accessions of Ahvaz (63.96 cm), the highest total fresh weight (8.16 gr) and the highest total dry weight (1.08 gr) were related to accession of Zahedan. It could be concluded that the salinity threshold for ten accessions, at which a considerable decrease in relative morphological traits per unit of salt, is more than 100 mM. Thus, identifying the physiological mechanisms and adjustments in ajwain under salinity as well as the threshold water potential at which physiological dysfunction begins to occur, would provide an understanding and help in developing adaptation strategies to protect this crop in the event of unexpected salinity.
